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Is there any algorithm for identifying the noise in an image I have to identify whether the noise present in a mammogram image is guassian or salt& pepper.

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Exploit the fact that salt&pepper noise has only 2 values and median filter does excellent job in getting rid of it.

  • Filter your image with median filter
  • Find pixels where median filter did most of its job
  • Plot histogram of those pixels
  • Compute fraction of 0s and 1s

    threshold = 0.2; % adjust to perform best on your images
    im = imread('../lena.bmp');
    imd = double(im);
    imd = imd./max(max(imd));
    imdg = imnoise(imd,'gaussian');
    imdsp = imnoise(imd,'salt & pepper');
    subplot(2,2,1), imshow(imdg)
    subplot(2,2,2), imshow(imdsp)
    imdgf = medfilt2(imdg);
    imdspf = medfilt2(imdsp);
    g = imdg.-imdgf;
    sp = imdsp.-imdspf;
    gm = abs(g)>threshold;
    spm = abs(sp)>threshold;
    subplot(2,2,3), hist(imdg(gm))
    subplot(2,2,4), hist(imdsp(spm))
    waitforbuttonpress
    

Result

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